Comparator circuits for comparing signals with reference signals are well known in the art, see for example European Patent Publication EP 0,870,646 A1. Present FIG. 2 corresponding to FIG. 3a of the just mentioned European Patent Publication shows an example of a conventional comparator circuit that is used in an electronic blinker, for example for a vehicle. The terms "blinker" or "blinker circuit" in this context refer to that part of the circuit which generates directional or turn signals while the term "hazard flasher" refers to the circuit when it functions as a hazard indicator. These terms may be used in combination or interchangeably.
Present FIG. 2 shows a comparator circuit for an electronic blinker in which a voltage drop across a measuring shunt resistor represents the current flowing through the blinker circuit. The voltage drop is compared with reference voltages having different voltage levels. The various results of the comparing provide indications or informations regarding the operational status of the blinker circuit, for example whether blinker lamps or bulbs have failed, whether additional bulbs have been connected to the blinker circuit, for example the bulbs of a trailer or whether a short-circuit exists in the blinker circuit.
Referring to FIG. 2, the conventional comparator circuit 25 comprises an input terminal 26 that is connected to receive the above mentioned voltage drop from the output of the blinker circuit. The comparator circuit 25 has, for example, four comparators K.sub.1, K.sub.2, K.sub.3 and K.sub.4. One input of each comparator is connected in common to the input terminal 26. The other input of each comparator is connected to a different reference voltage V.sub.ref1, V.sub.ref2, V.sub.ref3, and V.sub.ref4. These different reference voltages are generated by respective voltage divider circuits 33, only one of which is shown in FIG. 2. The output of each comparator is connected to a respective separate signal debouncing circuit 27, 28, 29 and 30. The outputs of the debouncing circuits in turn are connected to respective inputs IN.sub.1, IN.sub.2, IN.sub.3 and IN.sub.4 of a central control unit 31 for further processing. Each comparator with its respective reference voltage V.sub.ref1, V.sub.ref2, V.sub.ref3 and V.sub.ref4 forms thus a discrete stage in the circuit. The reference voltages V.sub.ref1, V.sub.ref2, V.sub.ref3 and V.sub.ref4 can be generated in any desirable manner, for example with the help of the above mentioned voltage dividers 33 connected with one terminal 32 to a supply voltage and with the other terminal 34 to a reference potential, preferably ground. The size and arrangement of the resistors 33' and a rectifier 33" will be selected in accordance with the required different reference voltage levels or thresholds.
The just described conventional circuit arrangement has the disadvantage that each discrete stage requires its own comparator, its own reference voltage supply circuit, and its own debouncing circuit, whereby the circuit component requirements multiply rapidly when several input signals are to be compared with a plurality of reference voltages. While the circuit components may be identical circuit components, they still increase the efforts and expense for such conventional circuits and make the respective printed circuit chips more expensive.